In the abdominal ganglion of Aplysia there is an identified cholinergic interneuron (L10) which has chemical synaptic input on a large number of other neurons. It is electrically coupled to two identified small neurons, one of which (L20) has been studied recently and found to have presynaptic modulatory effects on the release of transmitter from the various terminals of L10. Preliminary morphological investigations with cobalt injections into L20 have revealed that this neuron sends its axon toward the left connective and arborizes in the area of the bag cells containing the hormone that induces egg laying in Aplysia. On the basis of these findings, the purpose of this proposal is: 1) To investigate in more detail the electrophysiological and morphological interrelationships between the various branches of L10 and L20. 2) To search for possible synaptic connections between the bag cells and L20. 3) To study the effects of L10 and L20 activation on the follower neurons of L10 on some specific behavior responses such as cardivascular and gill withdrawal activities. Conventional electrophysiological techniques of recording and stimulating L10, L20 and two follower neurons of L20 at a time will be carried out. Similarly, the bag cells will aso be studied in relation to L20 activity. Morphological studies will involve the injection of cobalt and horseradish peroxidase into L20 and L10 to further elucidate the possible anatomic connection of L20 axons with other neurons. These studies will provide a background for further investigations relating the activity of specific neurons or clusters of neurons that mediate certain behavioral responses to the role of L10 and L21 activiy in the general integrative behaviors controlled by the neurons of the abdominal ganglion.